This invention relates to a rub link assembly for a dragline bucket and, more particularly, to a link assembly which features a rotatable collar so as to develop a rolling as contrasted to a scraping action as the hoist chain engages the bucket sides.
In the operation of a dragline bucket the hoist chain rubs against the sides of the bucket which can result in increased wear of the lower hoist chain. If this is not caught in time, serious damage could occur.
A previous effort to avoid this difficulty is seen in co-owned U.S. Pat. No. 3,181,257 which featured a twisted chain with increased amounts of metal at points of high wear. This has not proved to be a suitable solution and over the intervening years, operators have had to contend with this problem utilizing conventional chain.
A search of the prior art revealed no material teaching--a representative reference being U.S. Pat. No. 4,411,132 having to do with a special link for use with a windlass.
According to the invention, the rub link assembly replaces a link or links of the lower hoist chain on a dragline bucket and includes a rotating collar affixed to a plastic bushing which allows easy rotation about the central shaft link. When the rub link assembly is scraped along the side of a dragline bucket as it is in each dumping operation, the outer rotating collar spins about the shaft link and the entire assembly rolls along the side of the bucket, instead of scraping. Due to the advantage of rolling friction versus sliding friction, this assembly greatly reduces the wear caused by the chain scraping the side of the bucket--the life of both the chain and the contact area of the bucket is substantially increased. Further, the assembly can be rebuilt and reused in a new chain.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.